Communications and information technology equipment is commonly mounted in racks or enclosures. Equipment racks and enclosures are used to contain and to arrange communications and information technology equipment, such as servers, CPUs, networking equipment and storage devices in small wiring closets as well as equipment rooms and large data centers. A standard rack typically includes front-mounting rails to which multiple units of equipment, such as servers, are mounted and stacked vertically within the rack. A standard rack can be sparsely or densely populated with a variety of different components including components from different manufacturers.
Most rack-mounted communications and information technology equipment consumes electrical power and generates heat. The heat collectively generated in densely packed equipment racks can have adverse effects on the performance, reliability and useful life of the equipment in the racks. Accordingly, air cooling systems are often a part of an efficient data center design. In particular, many air conditioning (e.g. cooling) systems, such as described in U.S. Pat. No. 6,374,627, include a raised floor to facilitate the system's air cooling and circulation functions. These systems typically use open floor tiles and floor grilles, perforated tiles, or vents to deliver cool air into the room of racks from the air passageway disposed below the raised floor of an equipment room. Perforated tiles are typically located in front of the equipment racks and enclosures. The cool air flows from below the raised floor to the front side of the equipment racks or enclosures.
Rack-mounted equipment is often cooled by air that flows along a front side or air inlet side of a rack, through the rack, and out the rear or exhaust side of the rack. Often, the rate of the airflow across the heat generating components within the rack is dependent on the size and speed of one or more fans located within the equipment Consequently, the ability for the airflow to transfer heat away from the heat-sensitive components is heavily dependent on the inlet temperature of the air.
A common configuration of equipment in a data center has the racks in rows, where the inlet sides of the rows are arranged face to face. Grilles or perforated tiles are located in the raised floor structure between the two faces of the rows. This configuration is commonly called a “cold aisle” because the cool air from the air cooling system flows through the raised floor, through the perforated tiles and into an aisle between the rows. The cool air is then drawn into the rack mounted equipment and exhausted to the space behind (typically a “hot aisle”) or above the rows.
In an effort to provide an inlet air temperature that is sufficient to adequately cool large amounts of rack-mounted components, the capacity of a data center air conditioner may provide a combination of cold air at a high flow rate. Such high capacity air conditioners often use additional humidification/de-humidification systems to control the moisture in the air in the data center. Such humidification/de-humidification systems can be expensive to install and operate.